Modeling the energy cost of applications on portable wireless devices

Abstract

Extending the battery life of portable wireless devices has been in the focus of researchers for close to a decade. Several energy management techniques have been investigated at different levels of system design -- starting from silicon at the bottom to application design at the top, with communication protocols and operating system in between. In this paper, we present a model to estimate the energy cost of an application running on a portable wireless device. To develop the cost model, we partition a wireless device into two components, namely, computation and communication. Each component is modeled by a state-transition diagram. Two attributes are associated with each state: an average power cost and a state residence time. The cost of each state of the state-transition diagrams is validated by actual measurements. For a constant voltage supply, the average power cost of a state is denoted by the average current drawn by the component. The state residence times are estimated from the behavior of applications. The cost model has been validated by performing actual measurement of energy cost. We find that the estimated cost and the actual energy cost are within 5-10% of each other. This study will help us in improving the design of energy efficient software for portable devices. Moreover, the energy consumption breakdown into components will be an essential guide for future research in energy management of hardware and software systems.